function Ajax($method, $url, $parmas) {
    // 使用Promise
    return new Promise(function (resolve, reject) {
        let xhr = new XMLHttpRequest();
        let str = '?';
        if ($parmas) {
            for (let key in $parmas) {
                str += `${key}=${$parmas[key]}&`
            }
        }

        if ($method.toUpperCase() === 'GET') {
            xhr.open($method, $url + str.slice(0, -1));
            xhr.send();
        } else {
            xhr.open($method, $url);
            xhr.setRequestHeader('content-type', 'application/json');
            xhr.send(JSON.stringify($parmas));
        };

        xhr.addEventListener('readystatechange', function () {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    //返回成功
                    resolve(JSON.parse(xhr.response));
                } else {
                    // 返回错误
                    reject(JSON.parse(xhr.response));
                }
            }
        })
    })
}